Shanghai Institute for Minimally Invasive Therapy, University of Shanghai for Science and Technology, 516 Jungong Road, 200082, Shanghai, China.
Lasers Surg Med. 2021 Dec;53(10):1395-1412. doi: 10.1002/lsm.23420. Epub 2021 May 26.
Radiofrequency (RF) energy exposure refers to a popular non-invasive method employed to generate heat in cutaneous and subcutaneous tissues. RF thermal stimulation of adipose tissue has been considered to cause adipocyte metabolism and enzymatic degradation of triglycerides into free fatty acids and glycerol. Bipolar mode (BM) has achieved extensive applications in clinical studies on RF fat dissolution, whereas BM has a less penetration depth than monopolar, result in a higher RF voltage that may be required to increase power to the deeper fat layer of the subcutaneous tissue, and improper power control may easily cause the skin layer to be thermally damaged. To tackle down the mentioned defect, a novel phase-shift angle mode (PM) was proposed in this study based on double-channel bipolar RF. By employing the finite element method (FEM) and performing the ex vivo experiment, the effectiveness of BM was compared with that of PM in RF fat dissolution on subcutaneous tissue. In addition, this study attempted to develop reasonable phase-shift angles capable of achieving fat dissolution effects, while the RF energy of which would not cause the skin layer to be thermally damaged.
STUDY DESIGN/MATERIALS AND METHODS: Two electrode spacings (1 and 2 cm) were applied in BM (BM-1 cm and BM-2 cm, respectively), and six phase-shift angles (i.e., 30°, 60°, 90°, 120°, 150°, and 180°) were set in PM (i.e., PM-30°, PM-60°, PM-90°, PM-120°, PM-150°, and PM-180°). In addition, COMSOL was adopted to conduct a finite element analysis for achieving thermoelectric coupling. Ex vivo experiments were performed with a self-developed double-channel bipolar RF device, through which up to two adjustable phase-shift angle sinusoidal voltages could be generated. Such a device was isolated with a transformer and then connected to four electrodes with a 5 mm diameter contacting the ex vivo porcine abdominal tissue.
Under the RF voltage amplitude of 30 V, and after 1800 seconds of RF heating, no thermally damaged area was formed in the tissue in BM-1 cm and BM-2 cm; in PM-30°, PM-60°, and PM-90°, thermally damaged areas were formed in the fat layer, while the skin layer was not located in the thermally damaged area. Moreover, the temperature in the thermally damaged area attributed to the mentioned three conditions may satisfy the requirement of fat dissolution temperature.
Under the identical RF voltage and heating time, PM is easier to cause the fat layer of the subcutaneous tissue to be thermally damaged as compared with BM. Accordingly, PM may be enabled to achieve the fat dissolution effect under a relatively low RF voltage as opposed to BM, thus avoiding the possibility of thermal damage of the skin layer attributed to the use of higher RF voltage. In PM, different phase-shift angle significantly affects the electrical and thermal properties of RF energy applied on subcutaneous tissue; the phase-shift angle of RF voltage is likely to be regulated for fat dissolution effect, while the RF energy of which will not cause the skin layer to be thermally damaged.© 2021 Wiley Periodicals LLC.
射频（RF）能量辐射是一种广泛应用的非侵入性方法，用于产生皮肤和皮下组织的热量。RF 对脂肪组织的热刺激被认为会引起脂肪细胞代谢和甘油三酯的酶解为游离脂肪酸和甘油。双极模式（BM）已在 RF 脂肪溶解的临床研究中得到广泛应用，而 BM 的穿透深度比单极模式低，导致需要更高的 RF 电压才能增加到皮下组织较深脂肪层的功率，并且不当的功率控制可能容易导致皮肤层热损伤。为了解决这个问题，本研究基于双通道双极 RF 提出了一种新的相移角模式（PM）。通过使用有限元方法（FEM）和进行离体实验，比较了 BM 和 PM 在 RF 脂肪溶解对皮下组织的效果。此外，本研究试图开发合理的相移角，以实现脂肪溶解效果，同时 RF 能量不会导致皮肤层热损伤。
研究设计/材料和方法：在 BM 中应用了两种电极间距（1 和 2 cm）（分别为 BM-1 cm 和 BM-2 cm），并在 PM 中设置了六个相移角（即 30°、60°、90°、120°、150°和 180°）（即 PM-30°、PM-60°、PM-90°、PM-120°、PM-150°和 PM-180°）。此外，采用 COMSOL 进行热电耦合的有限元分析。通过自行开发的双通道双极 RF 装置进行离体实验，该装置可产生多达两个可调相移角正弦电压。这种装置通过变压器隔离，然后通过四个直径为 5mm 的电极与离体猪腹部组织接触。
在 30V 的 RF 电压幅度下，经过 1800 秒的 RF 加热后，在 BM-1 cm 和 BM-2 cm 中组织中没有形成热损伤区域；在 PM-30°、PM-60°和 PM-90°中，脂肪层形成了热损伤区域，而皮肤层未位于热损伤区域中。此外，由于上述三种情况，热损伤区域的温度可能满足脂肪溶解温度的要求。
在相同的 RF 电压和加热时间下，PM 比 BM 更容易导致皮下组织的脂肪层发生热损伤。因此，与 BM 相比，PM 可以在相对较低的 RF 电压下实现脂肪溶解效果，从而避免由于使用较高的 RF 电压而导致皮肤层热损伤的可能性。在 PM 中，不同的相移角会显著影响施加于皮下组织的 RF 能量的电和热特性；RF 电压的相移角可能会被调节以获得脂肪溶解效果，同时 RF 能量不会导致皮肤层热损伤。
